<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>滚动条</title>
<style type="text/css">
*{ margin:0; padding:0;}
p{ height:1000px;}
#mainBox{ width:400px; height:500px; border:1px #bbb solid; position:relative; overflow:hidden; margin:50px auto;}
#content{ height:2500px; position:absolute; left:0; top:0; background:url(http://files.jb51.net/file_images/article/201510/20151026113716032.jpg) }
.scrollDiv{ width:18px; position:absolute; top:0; background:#666; border-radius:10px;}
</style>
</head>
<body>
<div id="mainBox">
 <div id="content"></div>
</div>
<p></p>
<script type="text/javascript">
var doc=document;
var _wheelData=-1;
var mainBox=doc.getElementById('mainBox');
function bind(obj,type,handler){
 var node=typeof obj=="string"?$(obj):obj;
 if(node.addEventListener){
  node.addEventListener(type,handler,false);
 }else if(node.attachEvent){
  node.attachEvent('on'+type,handler);
 }else{
  node['on'+type]=handler;
 }
}
function mouseWheel(obj,handler){
 var node=typeof obj=="string"?$(obj):obj;
  bind(node,'mousewheel',function(event){
   var data=-getWheelData(event);
   handler(data);
   if(document.all){
    window.event.returnValue=false;
   }else{
    event.preventDefault();
   }
  });
  //火狐
  bind(node,'DOMMouseScroll',function(event){
   var data=getWheelData(event);
   handler(data);
   event.preventDefault();
  });
  function getWheelData(event){
   var e=event||window.event;
   return e.wheelDelta?e.wheelDelta:e.detail*40;
  }
}
function addScroll(){
 this.init.apply(this,arguments);
}
addScroll.prototype={
 init:function(mainBox,contentBox,className){
  var mainBox=doc.getElementById(mainBox);
  var contentBox=doc.getElementById(contentBox);
  var scrollDiv=this._createScroll(mainBox,className);
  this._resizeScorll(scrollDiv,mainBox,contentBox);
  this._tragScroll(scrollDiv,mainBox,contentBox);
  this._wheelChange(scrollDiv,mainBox,contentBox);
  this._clickScroll(scrollDiv,mainBox,contentBox);
 },
 //创建滚动条
 _createScroll:function(mainBox,className){
  var _scrollBox=doc.createElement('div')
  var _scroll=doc.createElement('div');
  var span=doc.createElement('span');
  _scrollBox.appendChild(_scroll);
  _scroll.appendChild(span);
  _scroll.className=className;
  mainBox.appendChild(_scrollBox);
  return _scroll;
 },
 //调整滚动条
 _resizeScorll:function(element,mainBox,contentBox){

  console.log(element);

  console.log(mainBox);

  console.log(contentBox);

  var p=element.parentNode;
  var conHeight=contentBox.offsetHeight;
  var _width=mainBox.clientWidth;
  var _height=mainBox.clientHeight;
  var _scrollWidth=element.offsetWidth;
  var _left=_width-_scrollWidth;
  p.style.width=_scrollWidth+"px";
  p.style.height=_height+"px";
  p.style.left=_left+"px";
  p.style.position="absolute";
  p.style.background="#ccc";
  contentBox.style.width=(mainBox.offsetWidth-_scrollWidth)+"px";
  var _scrollHeight=parseInt(_height*(_height/conHeight));
  if(_scrollHeight>=mainBox.clientHeight){
   element.parentNode.style.display="none";
  }
  element.style.height=_scrollHeight+"px";
 },
 //拖动滚动条
 _tragScroll:function(element,mainBox,contentBox){
  var mainHeight=mainBox.clientHeight;

  element.onmousedown=function(event){

   var _this=this;

   var _scrollTop=element.offsetTop;

   var e=event||window.event;

   var top=e.clientY;
   //this.onmousemove=scrollGo;
   document.onmousemove=scrollGo;

   document.onmouseup=function(event){
    this.onmousemove=null;
   }

   function scrollGo(event){

    var e=event||window.event;

    var _top=e.clientY;

    var _t=_top-top+_scrollTop;
    
    if(_t>(mainHeight-element.offsetHeight)){
     _t=mainHeight-element.offsetHeight;
    }
    if(_t<=0){
     _t=0;
    }
    element.style.top=_t+"px";
    contentBox.style.top=-_t*(contentBox.offsetHeight/mainBox.offsetHeight)+"px";
    _wheelData=_t;
   }
  }
  element.onmouseover=function(){
   this.style.background="#444";
  }
  element.onmouseout=function(){
   this.style.background="#666";
  }
 },
 //鼠标滚轮滚动，滚动条滚动
 _wheelChange:function(element,mainBox,contentBox){
  var node=typeof mainBox=="string"?$(mainBox):mainBox;
  var flag=0,rate=0,wheelFlag=0;
  if(node){
   mouseWheel(node,function(data){
    wheelFlag+=data;
    if(_wheelData>=0){
     flag=_wheelData;
     element.style.top=flag+"px";
     wheelFlag=_wheelData*12;
     _wheelData=-1;
    }else{
     flag=wheelFlag/12;
    }
    if(flag<=0){
     flag=0;
     wheelFlag=0;
    }
    if(flag>=(mainBox.offsetHeight-element.offsetHeight)){
     flag=(mainBox.clientHeight-element.offsetHeight);
     wheelFlag=(mainBox.clientHeight-element.offsetHeight)*12;
    }
    element.style.top=flag+"px";
    contentBox.style.top=-flag*(contentBox.offsetHeight/mainBox.offsetHeight)+"px";
   });
  }
 },
 _clickScroll:function(element,mainBox,contentBox){
  var p=element.parentNode;
  p.onclick=function(event){
   var e=event||window.event;
   var t=e.target||e.srcElement;
   var sTop=document.documentElement.scrollTop>0?document.documentElement.scrollTop:document.body.scrollTop;
   var top=mainBox.offsetTop;
   var _top=e.clientY+sTop-top-element.offsetHeight/2;
   if(_top<=0){
    _top=0;
   }
   if(_top>=(mainBox.clientHeight-element.offsetHeight)){
    _top=mainBox.clientHeight-element.offsetHeight;
   }
   if(t!=element){
    element.style.top=_top+"px";
    contentBox.style.top=-_top*(contentBox.offsetHeight/mainBox.offsetHeight)+"px";
    _wheelData=_top;
   }
  }
 }
}
new addScroll('mainBox','content','scrollDiv');
</script>
</body>
</html>
